Light-weight sandwich panel construction employing a honeycomb core sandwiched between faceplates has been highly useful for various aerospace applications such as the manufacture of space vehicle and satellite components. However, the application of such panels to the primary and secondary structures of ground-based airplanes and helicopters has resulted in significant maintenance problems. For example, during the past twenty years of service experience, very high frequency of repair has been reported, due, for example, to problems with moisture retention, corrosion, ineffective edge seals and unbonding of the faceplates from the cores. Moreover, during repair work, further unbonding of the faceplates from the core can result from high vapor pressure produced by the heating process used to cure the repair material. Thus, any comparable substitute to a honeycomb sandwich construction that eliminates or reduces the moisture retention and unbondings problem would be beneficial.
In U.S. Pat. No. 5,348,601 issued to Hemen Ray on Sep. 20, 1994, there is disclosed a low-density sandwich construction with an open core that makes it self-venting. It comprises corrugated strips having planar peaks and troughs, arranged adjacent to and parallel with each other, with the peaks and troughs of adjacent strips being 180 degrees out-of-phase with each other. This creates a plurality of passage-ways through which moisture can escape. Such a construction has good bending strength in the direction perpendicular to the corrugated strips, but less bending strength in the transverse direction.
In U.S. Pat. No. 5,162,143 issued to Porter on Nov. 10, 1992, there is disclosed a sandwich construction having a core which is made up of a plurality of criss-crossed corrugated strips. The corrugated strips cross at their peaks and troughs. To manufacture the construction, forming protrusions are positioned on a base, and the corrugated strips are placed over the protrusions to form the peaks of the corrugations. One protrusion is required for each peak crossing point. The criss-crossed strips are then cured to form the core of the sandwich construction. The forming protrusions are then removed, and face sheets are adhesively bonded to the core. This construction thus does not overcome the face sheet unbonding problem from which sandwich constructions suffer.